Cathode for discharge devices



Jam-5,1937. J. w. MARDEN CATHODE FOR DISCHARGE DEVICES Filed June 14, 1933 INVENTOR J: M MflFDE/V 5'1 1 ATTORNEY l'l-ED YATES A'E'EN'E' OFFICE CATHODE FOR DISCHARGE DEVICES John W. Marden, East Orange, N. J assignor, by mesne assignments, to Westinghouse Electric and Manufacturing Company, East Pittsburgh, Pa... a corporation of Pennsylvania Application June 14, 1933, Serial No. 675,671

March 21, 1930 and assigned to the same assignee which is again wound to provide what may be 5 as the present invention. termed a coiled coil. The outer coil may be made The above mentioned application shows and by welding or otherwise securing an end [2 of a describes a device in which two thermionically wire [3 to a terminal of the coiled coil. The.

v I activeelectrodes are provided and wherein the heater element may, however, be in the form of difierence of potential is produced between the a straight length of helically coiled filament or 10 electrodes and means are furnished to heat the may be an uncoiled wire of suitable resistance. electrodes to electron emission temperature to In accordance with the present showing the produce a glow discharge. The electrodes are coiled coil may then be positioned in a forming enclosed in a sealed envelope containing an ionmandrel [4 having a core l5 to receive the coiled izable medium and each electrode is provided with coil and a slot l6 through which the wire I3 15 a pair of conductors to permit a flow of electrical may extend. When the coiled coil is in position energy for heating the electrodes to electron in the mandrel M the wire I3 may be wound emission temperature to produce a glow discharge about the mandrel as shown in Fig. 4 until an which is maintained by the flow of current across outer helical coil is formed. If desirable, the

the discharge. outer surface of the mandrel l4 may be provided 20 In the device above outlined a cathode or elecwith a helical groove or thread to serve as a guide trode is provided which consists of a mandrel for winding the outer coil to regulate the spacing having a helical winding of a wire which is coated thereof. with a thermionically active material. The en- Cathodes constructed in accordance with the tire electrode is heated directly by a flow of elecpresent invention may be mounted in a discharge 25 trical energy. device and, as shown in Fig. 1, such device may It is an object of the present invention to procomprise a bulb l1 sealed at IE to a flare tube [9 vide an improved form of cathode for a discharge having a press 20 and containing a suitable ionizdevice in which the electron emitting material is able medium; as for example mercury vapor.

heated directly. Lead wires 2|, 22 may be sealed in the press and 30 Another object of the invention is to provide extend into the bulb to serve as supports for the a cathode for a discharge device comprised of an cathodes. A cathode may be secured to the supinner and an outer metallic-coil. ports by having one end of the coiled coil elec- Another object of the invention is to provide trically connected to one support and the free 5 an indirectly heated cathode comprised of a helend of the outer coil secured to the other support. ical carrier for a thermionically active material. Connection between the coiled coil may be made Another object of the invention is to provide a prior to the operation of winding the outer coil method of making a cathode of the indirectly as shown in Fig. 3. It is to be understood howheated type. ever that a cathode may be constructed by mak- 40 Other objects and advantages of the invention. ing the coiled-coil heater and the outer winding 40 will be apparent from the following description as separate parts and in subsequently welding or together with the accompanying drawing in otherwise securing the parts together. which The outer coil may be made of about 20 to 31 Fig. 1 is a side elevational view of a pair of mil nickel, nickel wound tungsten, Monel or other cathodes constructed in accordance with the suitable base metal. The heater or coiled coil 45 present invention mounted in a bulb; may be of tungsten.

Fig. 2 is an enlarged view of the cathodes taken When the cathode is to be used in a lamp havin line IIII in Fig. 1; ing a drop of about 15 volts the heater element 10 Fig. 3 is a perspective view of the heater elemay consist of a non-sag tungsten space wound ment of a cathode showing a Wire connected coil wound on a 21 mil mandrel with about 125 50 thereto ready to be coiled about the cathode and turns per inch. The wire may be of a weight of Fig. 4 is a perspective view of a forming manfrom 21 to 22 /2 milligrams per 200 m. m, of drel for holding the heater coil and for forming length. The heater element may consist of l5 the outer winding therearound. m. m. coil length including about 75 turns of wire 7 Claims.

This invention relates to glow discharge lamps and relates more particularly to an electrode for a discharge device such as shown and described in copending application Ser. No. 437,659 filed A cathode constructed in accordance with the present invention may comprise a heater coil Ill having an enclosing helical winding or support I I for a thermionically active material.

The heater may be a helically wound wire wound as above described. When winding the outer coil the mandrel on which this coil is wound may be about 180 mils in diameter.

For the purpose of providing an electron emitting surface the outer coil may be sprayed or otherwise coated with a quick drying binder such as nitrocellulose in amylacetate, with the carbonates of the alkaline earth metals. The carbonates are stable in atmosphere and may be stored for indefinite periods Without detrimental effects. After the cathode assembly has been mounted within the bulb the carbonate coating is converted to the oxides of the alkaline earth metals by heating the cathode to a sufficiently high temperature. The method of providing a cathode with an electron emissive material, as above briefly given, is known in the art and may be varied to meet attending conditions.

It has been found that there are no'detrimental results if the heater receives some of the electron emissive material when the outer coil is sprayed since this deposit on the cathode is burned off when the heater reaches a high tern perature upon a flow of current.

The present invention provides an improved and simple cathode assembly for use in discharge lamps where it is desirable to support a thermionically active material for indirect heating. The structure shown may be constructed with a minimum amount of labor and at relatively low cost.

Although a preferred embodiment of the invention is shown and described herein it is to be understood that modifications may be made therein without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. An electric discharge lamp comprising a bulb, a press at one end of said bulb, a pair of electrodes disposed in parallel spaced relation, each of said electrodes including a pair of rigid support members extending from said press, a rigid helical coil having one end secured to one of said support members, a coating of electron emission material on said coil, another double helically coiled wire having one end secured to the other support wire and the other end secured to and supported on the free end of said rigid coil.

2. An electric discharge lamp comprising a bulb, a stem extending from one end of said bulb, a pair of elongated electrodes disposed in parallel spaced relation, each electrode including a pair of support wires secured in said press, a rigid helical coil having one end secured to one of said support wires and a less rigid coiled coil supported in concentric relation to said rigid coil by the other support Wire and held by the free end of said rigid coil.

3. An electric discharge lamp comprising a bulb, a stem extending from one end of said bulb, a pair of elongated electrodes disposed in parallel spaced relation, each electrode including a pair of support wires secured in said press, a rigid helical coil having one end secured to one of said support wires and a double helical coil disposed within and supported in concentric relation to said rigid coil by the other support wire and held in spaced relation to said rigid coil by the other end of said rigid coil.

l. A discharge lamp comprising a bulb, an ionizable medium within said bulb, a pair of electrodes disposed within said bulb and positioned in relatively close parallel spaced relation to produce a glow discharge therebetween when subjected to a voltage drop of sufficient potential, each of said electrodes comprising a rigid helical coil having a thermionically active material thereon, a conductive support member secured to one end of said rigid coil, a heater coil having one end secured to the other end of said rigid coil and another conductive support member connected to the other end of said heater coil, said conductive support members serving to permit a flow of electrical energy through said heater coil to heat said rigid coil and cause an electron flow by reason of a potential diiference between said electrodes, said electron flow causing an ionization of the gas to produce a glow discharge. 7

5. An electrode for a discharge device comprising a rigid helical coil having thereon a coating of thermionically active material, two rigid support members, said coil having one end secured to one of said rigid support members, a flexible coil for heating said material, said coil having one end secured to the other rigid support member and the other end secured to and supported by the other end of said rigid helical coil.

6. An electric discharge lamp comprising a bulb, an ionizable medium in said bulb, a press at one end of said bulb, a pair of rigid support members extending from said press, a rigid helical coil having one end secured to one of said support members, a coating of electron emission material on said coil, another helical coil concentrically disposed within and disposed in spaced relation to said rigid coil for the passage of said medium between said coils, said other helical coil having one end connected to the other support member and the other end connected to and supported by the other end of said rigid coil.

'7. An electric discharge lamp comprising a bulb, a stem extending from one end of said bulb, a pair of support wires secured in said press, a rigid helical coil having one end secured to one of said support wires, a coating of emission material on said coil and a coiled coil connected to the other support wire and held in spaced re-- 

